Some people have poor blood circulation. Pointing a small fast fan at their arms will not cool their core.
Some people get dry eyes easily. Pointing a fan at their face will make them extremely uncomfortable.
Some people are extremely sensitive to temperature changes. They don’t want to be hot but pointing a 40 degree F stream of air at their chest will give them physical pain.
No, this isn’t a one size fits all problem/solution. The correct solution is actually to cool the whole car while allowing the user control over how to cool themselves by adjusting the fans/doors. It would be much better however if car manufacturers included better PID controllers as well as moisture sensors inside and outside the cabin to create better climate control. In a car that really shouldn’t be difficult, at least with the windows closed. It’s not like a house with multiple rooms that have different exposure to heating and cooling as well as sunlight.
I don't want to have cold hands, arms, and face, while my back and my feet sweat.
Surely if an air conditioner brings an indoor area to a given temperature (and humidity), it doesn't matter what the temperature is outside. So what gives? Is the air conditioner not powerful enough? Do people not want the inside to be as cold as in other locales, since they're used to the heat? The latter would make sense, but then I don't understand why you'd need to be blowing the vents directly at you.
Also with car A/C (or indoor spaces which take in a lot of direct sunlight), hotter days tend to be the result of greater insolation. If direct sunlight is hitting your skin on a clear summer day it has a significant warming effect which you would want to offset with more ambient or active cooling.
For example, you are out walking on cold ground. Your feet get cold while your core stays warm. This is ideal for keeping heat in your core. You may survive where those with "good" circulation would lose heat too fast.
Although this may be due to lower rate of blood circulation, there is another effect independent of circulation rate.
Heat-exchanger effects along limbs depending on the layout of your veins and arteries, which varies among people. The extreme example is penguins, whose feet are on ice yet their bodies retain heat because of heat exchange as blood circulates in their legs. It maintains a temperature differential along the legs. I'm not suggesting people have specific anatomical structure like penguins, rather I'm saying the natural variation in the placement of veins and arteries in human limbs will result in a range of heat-exchange factors among different people, which is a separate factor from circulation rate, and may indicates a thermally efficient body for some situations.
heat transfer is what makes you feel cool/warm, not temperature, and air flow promotes convection (as well as conduction). it's why metal feels cooler (or warmer) than plastic at the same temperature (e.g., differing heat transfer coefficients).
[0]: note that most car trips are less than ~15 minutes, at which point, all that heating/cooling is wasted as you flush it out the door.
Talking about energy efficiency: if your car trip is <15 minutes, then ideally you shouldn't be using a car at all!
That depends on where you live. It take me about 5-7 minutes to drive to the nearest store (a "Dollar General" store). That store is about 2.5 miles away, so about a 5 mile round trip. Average walking speed is about 3.2 mph, so a +2 hour trip walking it.
The next nearest store is about 10-12 miles away (a grocery store). Most of those miles are on a road with a 55mph limit but these are curvy hilly roads so probably closer to a 40-45 mph average. That's a +6 hour walk.
Riding a bicycle is akin to death wish on those 2 lane roads with no shoulder.
Assuming you live in an urban area, this seem like absolute madness to me. Does this not represent a huge opportunity for someone to start a local grocery store business?
I have never lived further than 15 minutes walk to the local grocery store (and I considered that a pretty inconvenient location). Where I live now I have a 2 local shops ~1 minute walk away, with a small high street with a small supermarket ~10 minutes walk away. And I would say this is pretty typical across the entirety of urban/suburban UK.
> Does this not represent a huge opportunity for someone to start a local grocery store business?
Those stores do mostly exist where they are viable. The limiting factors are:
1. many of those neighborhoods don't have commercial space, and are filled with people who live there specifically because they do not want to live by commercial property, and support zoning regulations to keep grocery stores from being built besides their property.
2. because many people do have cars, neighborhood grocery stores are sometimes at a commercial disadvantage, because many of their potential customers can easily drive to stores with greater selection.
I do like living in more lively neighborhoods, and I picked one where I do have two small grocery stores within 15 minutes walking distance. The thing is, they're both ethnic grocery stores with limited selections. I try to support them when I can but to get everything that I want to buy in one shopping trip, it's much quicker and easier to drive out of my neighborhood to a much larger store.
but yes, for those majority short trips, the wind in your hair on a (electric) bike/scooter is likely just as cooling, and the trip likely no longer.
Maybe electric vehicles could be an incentive to downsize vehicles?
That's not called for.
> you're sitting uncomfortably for 10-15 minutes waiting for that temperature to be reached
It doesn't take that long, and you can compromise by hitting yourself with some of the full-power cooling until the cabin reaches a comfortable temperature.
> heat transfer is what makes you feel cool/warm, not temperature, and air flow promotes convection (as well as conduction).
Heat transfer yes, but everywhere on the body. You can't just look at the total.
Telling someone that tomato is a more vibrant red than chicken, will not compel them to prefer the taste of a tomato to the taste of chicken. (In this example the “correlation” bit doesn’t apply, but, whatever.)
This material is a passive method that I think rather soon recoups any extra energy expended during manufacturing.
Summer has similar situations. Point a small fan at yourself and you can save a lot on cooling the entire unit. A fan is blowing a gentle breeze across my hands right now (tip: aim it across the keyboard; it cools the laptop and you, and it doesn't dehydrate me). As long as the ambient temperature is below about 85, I'm fine. Think of it: 80 degrees, in the shade, with a breeze. That's pretty nice.
This acts as sort of a regulator for the system, which ultimately ends up reducing the load on the compressor as the evaporator is colder.
So while the compressor runs at one stage in the sense of it being directly driven by the engine, the resistance to spin the compressor varies based on the load of the AC system.
in the same vein, most people's behavior around heating/cooling is comically misguided and inefficient. most people believe temperature is what we're trying to control, and that's driven by how weather reports, climate controls, and even our language ("it's hot!") emphasize temperature (which isn't nefarious, and makes sense in their separate, respective domains) rather than heat transfer, which is what we're really after.
this is most evident in cars, where folks point air vents away from themselves while running the a/c (or heat) full blast, rather than pointing the vents at themselves and running at a lower speed. the former is based on the idea that the whole car's interior temperature needs to be lowered (or raised) for effective heat transfer away from (or to) the body, which is incorrect and inefficient. pointing the vents at you (on bare skin ideally) promotes heat transfer immediately instead of waiting to create a big enough temperature differential to do the same work.